Rewards programs have been surging in recent years, as credit card companies have tried to find ways to make their cards more attractive to potential users. Most credit cards offer airline miles, cashback promotions and a variety of other perks designed to get and keep customers.

Celebrities such as Samuel Jackson and Jennifer Garner are used to tout the benefits of reward cards, bringing in millions of new users.

But many people aren’t aware of their current program rewards and fail to redeem them, or just don’t think it’s worth the time or effort. While credit card companies benefit from such non-use because they don’t have to shell out the money to provide the rewards, a recent study by NextAdvisor found that confusion is causing consumers to leave money on the table when they don’t keep up with their card’s rewards.

More than half the people surveyed by NextAdvisor reported that they find frequent flier programs confusing, and about four in 10 Americans admit to having let their airline miles expire unused.

Of course, redeeming airline miles and hotel points can be infuriatingly complicated. Years ago, while trying to arrange a family trip, I found that my airline miles were blacked out for dates when I wanted to travel, and there were all kinds of stipulations that limited when and how I could use them. Some credit cards promise to make this process easier, but all programs have limitations.

“By not redeeming miles, rewards or loyalty points, consumers are literally leaving money on the table,” said NextAdvisor analyst Julie Myhre-Nunes in a blog post. “That’s why it’s important for you to take the time to find the programs and credit cards that best suit your needs.”

Many financial experts suggest consumers shop around on a regular basis for cards with better rewards or special promotions that can save money. A similar study last year found that about 32 million U.S. cardholders haven’t changed their primary card in more than a decade.

Not only do cardholders not understand the confusing fine print on many programs but they also wouldn’t know how to redeem their rewards if they did. More than a third of frequent-flyer program participants and hotel loyalty program participants said they don’t know how to redeem offers, even those that provide cash back benefits. Even users of cards that provide statement credits for purchases often fail to redeem them.

As to who’s to blame for the confusion, Myhre-Nunes noted, credit card companies’ policies are often not clear or easy to understand.

“While consumers are definitely out of the loop when it comes to their rewards credit cards, they aren’t the only ones to blame,” she said. “Since credit card issuers are in control of their cards’ rewards and redemption opportunities, it’s clear that some issuers are also failing to educate their cardholders.”

For those who are relatively uninitiated into the credit-card marketing game, perhaps it’s wrongheaded to select a card just for the rewards, anyway. Competition has created a buyer’s market for consumers with decent-to-excellent credit, so you should be able to easily find a card with low interest rates, nonexistent annual fees and widespread usability. If a card can do that, and at the same time accumulate miles, bonus cash and hotel points, it’s probably a good deal all around.